Keyboard for musical instruments



May 10, 1938.

L. HAMMOND KEYBOARD FOR MUSICAL INSTRUMENTS Filed July 18, 1956 2 Sheets-Sheet l May 10, 1938. 1 HAMMOND 2,117,002

KEYBOARD FOR MUSICAL INSTRUMENTS Filed July 18, 1936 2 Sheets-Sheet 2 M I| 0 In N" @l W l Patented May 10,' 1938 UNITED STATES PATENT OFFICE 15 Claims.

The present invention relates generally to keyboards for musical instruments, such as pianos, organs and the like, and more particularly to improvements ln the construction of the keys, the method of making them, and in the means for y mounting and assembling the keys.

It is an object of the present invention to provide an improved key for the manuals or keyboards of organs, planos and the like, which is molded of a phenol condensation product or casein compound or other suitable plastic.

A further object is to provide an improved key bar, and to provide improved means for securing the key to the key bar.

A further object ls to provide an improved key for musical instruments, which is made of a molded plastic, and in which the molded plastic surface forms the finished playing surface.

A further object is to provide an improved molded plastic key in which the key is of inverted box-like structure and in which the inner surfaces are utilized to guide the key.

A further object is to provide an improved means for adjusting keys of a keyboard for unlform touch.

A further object is to provide an improved means for pivotally mounting the keys of a keyboard, and for guiding the keys in their pivotal movement.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Fig. 1 is a vertical cross-sectional view through one of the black keys of the keyboard;

Fig. 2 is a vertical sectional view taken on the line 2--2 of Fig. 1;

Fig. 3 is a vertical sectional view taken on the line 3-3 of Fig. 6 showing one of the key guides;

Fig. 4 is a vertical sectional view taken on the line 4-4 of Fig. 5 showing the fulcrum and pressure adjusting means for the key bars;

Fig. 5 is a fragmentary plan view of one octave of the keyboard;

Fig. 6 is a plan view of the guide comb;

Fig. '7 is a vertical sectional view of one of the white keys, taken on the line 1-1 of Fig. 5; and

Fig. 8 is a sectional view taken on the line 8-8 of Fig. '1.

The present invention is illustrated in conjunction with parts of an electrical musical instruent, such as disclosed in my prior Patent No. ,956.350, granted April 24, 1934, and in my copending application Serial No. 76,157, filed April 24, 1936.

In the course of preparing to manufacture the instrument of the type shown in my aforesaid patent, I discovered that the keyboards of the conventional type used on pianos and organs would not be fully satisfactory because of their high cost of manufacture, the possibilities of mis- 5 alignment due to wear and warping, and because of the relatively inaccurate method by which the keys were mounted for pivotal movement.

As far as I am aware, keyboards for musical instruments of the type represented by the piano and organ have from historic times to the present been made of wood and covered with sheets of ivory, celluloid and the like, which were glued or otherwise cemented to the wood. The keys were thus necessarily of considerable weight and inertia. It is of course desirable to make the key as light as possible so as to reduce its inertia and increase the speed with which it may be depressed and returned to normal position. 'Ihe speed of the return stroke of a key may be increased by increasing the spring or gravitational force utilized to return the key to normal position, but increasing this force likewise increases the force necessary to depress the key, with the result that with keys constructed in accordance with the standard practice followed in the industry, the choice lay between having the keys operable by a light touch, with a relatively slow return stroke, or having a faster return stroke by increasing the force required to depress the key. By making the keys very light in weight, I have been able to obtain the desired rapid return stroke while retaining the light touch.

According to my present invention, the keys are molded of a plastic compound and are made of 35 inverted box-like sections by which maximum strength and minimum weight are attained. The black keys may suitably be molded of a phenol condensation product and the white keys made of casein molding compound, although other 40 similar molding compounds may be utilized.

In Figs. 1 and 5, are shown pressed metal angles i0 and I2 which, at their ends, are bolted to side frame members i4, of which only one is shown in Fig. 5. suitably spaced along the hori- 40 zontal leg oi the angle il) are a plurality of studs i6, one for each key of the keyboard, these studs being riveted to the angle III and having upwardly projecting cylindrical portions I8 forming mountings for key bars 20. The upper end of 50 each of the studs i6 has a threaded portion 22 to receive an adjusting nut 24 by which the degree of compression of a spring 26 may be varied. Each of the compression coil springs 26 has its upper turn fitting in a suitable annular groove 28 formed in the adjusting nut and its lowermost turn resting in a depression 30 formed in the key bar 20. The nuts 24 are locked in adjusted position by a strip 32 made of wood or other suitable material and having a groove 34 embracing the ilats of the hexagonal surfaces of the row of adjusting nuts 24.

The key bars 20 are preferably a special shape extruded aluminum or aluminum alloy channel. fis best shown in Fig. 4, the bottom surface of the key bar is provided with a pair of beads 36 at its edges, these beads resting upon a fulcrum rod 38 which extends the length of the keyboard and is retained in position by resting between the studs i6 and the heads of cap screws 40 which are utilized to secure Vertical frame plates 42 to the horizontal leg of the angle l0.

As shown in Figs. l and 2, each of the black keys 44 is of inverted hollow box-like section having a rear wall 46 of relatively heavy crosssection, a pair of side walls 48 and a front end wall 50. The sidewalls 48 are joined by a relatively heavy web 52. The web 52 and the rear wall 46 are tapped to receive cap screws 54 and 56 respectively, by which the key 48 is secured to the key bar 20. The cap screw 54 fits snugly into the hole in the key bar formed to receive it, while the cap screw 56 has a loose t therein. Thus, when the key expands or contracts due to changes in thermal and moisture conditions, the rear cap screw 56 may shift very slightly relative to the key bar 20 to accommodate for expansion and contraction of the key. For this reason, the cap screws are not drawn up tightly, but are backed away a portion of a turn so that the lock washers placed beneath the heads of the cap screws resiliently hold the key against the key bar. It will be noted that the side walls 48 of the key bar rest upon the upper edges of the vertical walls of the channels 20, and that cylindrical bosses 57 formed on the Wall 46 and web 52 fit snugly in the channel of the key bar 20.

The white keys 58 are likewise formed in inverted box-like sections comprising a top wall B0, side walls 62, a relatively heavy rear wall 64, a thickened cross web 66 and relatively thin cross web 68. The rear wall 64 and the web 66 are tapped to receive cap screws l0 and 'I2 respectively, by means of which the key 58 is secured to the channel key bar 20. The wall 64 and web 66 are provided with cylindrical bosses i3 which fit into the channel of the key bar 20 and aid in holding the key in alignment with the bar. (The key bars 20 for the white keys are slightly shorter than the key bars for the black keys, as indicated by the dotted line in Fig. I.) It will be noted that the cap screw 12 ts snugly into the hole formed therefor in the key bar 28, while the cap screw 10 projects through a hole formed in the key bar 20 which is slightly larger in diameter than the cap screw. The key 58 is thus permitted to expand and contract upon changes in temperature and humidity and in doing so to shift the cap screw 'l0 slightly relative to the key bar 20. The setting up of undue strains and possible cracking of the key is thus prevented. The key illustrated in Figs. 7 and 8 is for the key A, and thus its forward portion 14 is widened. It will be understood that the shape of each of the White keys differs slightly from that of the others in the octave due to the irregularity in the spacing of the black keys. The forward wall 'I6 of the key is reenforced by a rib 'I8 and at its lower edge has a forwardly atraco@ projecting flange to limit upward and down'- ward movement of the key.

The keys are guided by teeth 82 forming part of a stamped sheet metal comb 83 which is secured to the forwardly projecting portions of the frame plate 42 by cap screws 85. The teeth 82 have rearwardly bent portions 84 at their upper ends, and strips of cotton fabric tape 86 are wound about these portions, the fabric being secured thereto by clips 88, each of which has a tooth 90 punched therefrom, the tooth fill being pressed through the tape 86 and projecting through an aperture 92 formed in the rearwardly projecting portion 84 of the tooth 82. The edges of the tape 86 thus engage with the inner walls of the keys 44 and 58 and form guides therefor to assure that they may swing in a vertical plane. Downward movement of the black keys is limited by a strip 94 of heavy felt which rests on the horizontal portion of the comb 83 and is held in position by a plurality of pins 96 which project through suitable holes punched in the felt strip. These pins are located in alignment with the white keys, so as not to interfere with the downward movement of the black keys. When one o! the black keys is moved downwardly, the projecting end of its key bar 20 is adapted to engage the felt strip 94, and upon upward movement, a felt pad 98 secured to a clip |00 is adapted to engage the lower surface of the clip 88 and limit upward movement of the key. The clip |00 is clamped between the key bar 20 and the projecting boss portion 51 of the web 52.

Downward movement of the white keys 58 is limited by engagement of the forwardly projecting flanges 80 of these keys with a felt strip |02, while their upward movement is limited by engagement of the flanges 80 with a felt strip |04. These strips |02 may be cemented or otherwise suitably secured to a metal strip |88 fastened to the frame plates 42 by cap screws |08, while the felt strip |04 may be secured to a suitably finished angle strip H6, which is fastened to the angle plate |2 by means of bolts 2.

A felt pad H4 is secured to each of the key bars by a pair of hollow rivets H8. These felt pads normally lie above the ends of switch actuators. The details of the switch and the operation of the actuators I I8 are fully disclosed in my aforesaid copending application, Serial No. 76,157, filed April 24, 1936.

It will be noted that the compression coil springs 26 are located very close to the fulcrum formed by the rod 38, and the springs may therefore be relatively strong without making the force necessary to depress the key too great. Since the lower surface of the key bar is provided with beads 36, and the spring is located centrally between these beads, the spring will tend to hold the key bar against tilting along its longitudinal axis. Compensation is automatically made for any wear which may take place at the fulcrum, either on the fulcrum rod 38 or upon the key bar 36 since the spring 26 will always maintain the key bar against the rod 38. The fingers 82 of the comb 84 very effectively prevent swinging or shifting of the keys in a horizontal plane about the axis of the studs I6. Due to this construction, wear at the fulcrum can never result in making the key noisy or permit the click at this point when the key is operated. The spring is very powerful relative to the weight of the parts, and thus no matter how rapidly the key may be operated there will be no tendency whatsoever for the key bar to be raised from contact with the fulcrum rod 38. The factthat the keys 4I and 5B are made hollow, makes it possible to use their inner surfaces as guide contacting ways, while the hollow, box-like construction at the same time assures maximum strength for a given weight of material.

By placing a predetermined weight at the forward ends of each of the keys, the degree of compression of the springs 26 can be readily adjusted by tightening or loosening the adjusting nuts 2l. In the production of these keyboards, the springs are given such a degree of compression as will assure the most rapid action compatible with lightness of touch. If, however, the user of the instrument desires more rapid action at the expense of lightness of touch, or vice versa, he may change the adjustment of the nuts 24 accordingly to secure any desired touch and action.

It will be noted that the key bars 20 are of channel shape with the open portion of the channel facing upwardly. 'I'his is a very convenient construction, since the hollow portion of the channel serves to receive the bosses 51 and I3 formed to receive the cap screws by which the keys are attached to the key bars, and furthermore, that the channel may receive the compression coil spring 26, and because of the latter fact, the pivot fulcrum may be located very close to the axis of the spring.

The keyboard of my present invention is relatively inexpensive to manufacture, because of ease and rapidity with which the parts may be assembled. Since the keys are molded with the desired smooth surface finish they require only a tapping operation before assembly to the key bars. All of the parts may easily be made to sufciently close limits to assure rapid and eilicient assembly of the keyboard.

While I have showin and described a preferred embodiment of my invention, it will be understood by those skilled in the art that numerous variations and alterations may be made in the inventionv disclosed without departing from the basic concept thereof. I therefore desire to include in the accompanying claims, all such modifications and variations as will be readily apparent to those skilled in the art by which substantially the results of my invention may be obtained in substantially the same way.

What I claim as new and desire to secure by United States Letters Patent is:

1. In a keyboard for musical instruments, the combination of a plurality of keys, a key bar secured to each of said keys and having a pair of spaced downwardly projecting portions, a common fulcrum member for a plurality of said keys, a compression coil spring normally pressing the downwardly projecting portions of said key bars against said fulcrum member, the axis of said spring being close to the axis of said fulcrum member and between the downwardly projecting portions of said key bars, means for individually adjusting the tension on said springs, and locking means common to a plurality of said adjusting means.

2. In a keyboard for musical instruments, the combination of a key, a channel-shaped key bar secured to said key and having a pair of spaced ribs on its lower surface, a fulcrum member extending transversely beneath said ribs and engaged by the latter, and a compression coil spring acting in the direction of a line passing between said ribs.

3. In a keyboard for musical instruments, the combination of a key made of a molded plastic compound, a key bar of metal, means for tightly securing one end and loosely securing the other end of said key to said key bar, a fulcrum for said key bar closely adjacent one end thereof. and a compression coil spring for holding said key bar against said fulcrum.

4. In a keyboard for musical instruments, the combination of a plurality of keys, a key bar secured to each of said keys, a fulcrum for said key bars, a spring located above each of said key bars and normally pressing its associated key bar downwardly against said fulcrum, means for individually adjusting the tension on said springs, and common means for locking all of said adjusting means.

5. A key for musical instruments of the piano and organ type comprising an integral thinwalled hollow box-like structure having an open bottom and formed of a nonvitreous plastic molding compound. v

6. A key for keyboards of the type used in pianos and organs comprising an inverted hollow box-like member having an open bottom and formed in one piece from a non-vitreous plastic molding compound.

'1. In a keyboard for musical instruments, an integral key comprising a hollow box-like member formed from a plastic molding compound, a pivotally mounted key bar secured to said key, and means directly engaging the inner walls of said key for guiding it during its oscillatory movement.

8. In a keyboard for musical instruments, a plurality of integral keys each comprising a hollow box-like member formed from a plastic molding compound and having a flange projecting therefrom, a pivotally mounted key bar secured to each of said keys, means directly engaging the inner walls of said keys respectively for guiding the keys during their oscillatory movement, and means engageable with the opposite sides of said flanges to limit the oscillatory stroke of the keys.

9. In a. keyboard for pianos, organs and the like, the combination of an integral hollow inverted box-like key structure formed from a plastic molding compound, a metallic key bar, means to fasten said key structure to said bar, said fastening means comprising means for substantially rigidly securing one portion of said key structure to said key bar and securing another portion of said key structure to said bar in a manner to permit slight movement of said latter portion relative to said key bar.

10. In a keyboard for musical instruments of the piano and organ type, the combination of a key bar having an opening in the rearward end thereof, a stud projecting through said opening, a spring surrounding said stud and having one end pressed against the upper horizontal surface of said key bar, a pivot fulcrum rod located adjacent said stud, and an adjusting nut threaded on said stud and engaging the other end of said spring for Varying the compression thereof.

1l. In a keyboard for instruments of the piano and organ type, the combination of a key bar of generally channel shaped cross-section having beads along the edges of the web portion thereof, a key secured to' one end of said bar, a fulcrum rod located beneath said key bar, said key bar having the beads thereof resting upon said rod, and a spring engaging said key bar near said fulcrum at the end of said bar opposite said key, said spring being operable to return the key after it has been depressed and to prevent tilting of the key about its longitudinal axis.

12. A key assembly for musical instruments of the piano and organ type, comprising a key :formed 1from a plastic molding compound, said key having downwardly projecting bosses, a channel shaped metallic key bar of sufficient width to receive said bosses between its anges, and screws projecting through said key bar and threaded in said bosses for securing said key to said key bar.

13. In a keyboard for musical instruments of the piano and organ type, the combination of a key bar having an opening in the rearward end thereof, a stud projecting through said opening, a spring surrounding said stud and pressing downwardly against the upper horizontal surface of said key bar, and a pivot fulcrum rod located adjacent said stud and beneath said bar.

lll. A key for musical instruments of the piano and organ 'type comprising, an elongated body formed from a plastic molding compound, a metallic key bar, means for securing one end of said body to said bar to prevent relative movement therebetween, and means for loosely securing the other end of said body to said bar, whereby upon expansion and contraction of said body the latter end thereof may move longitudinally with respect to said bar.

15. A key for keyboards of the type used in pianos and organs and comprising an inverted hollow box-like member formed in one piece from a plastic compound and having a reinforcing web provided with a tapped hole to receive an attaching screw, a key bar, and a screw projecting through said key bar and threaded in said tapped hole for securing said member to said key bar.

LAURENS HAMMOND. 

